The present invention relates to a system for monitoring the engine oil pressure of an engine-driven vehicle.
It is now possible, due to microprocessor technology, to monitor various vehicle operating parameters according to complex criteria. For example, a transmission oil pressure monitoring system is described in copending U.S. patent application, Ser. No. 379,230, filed May 17, 1982, a clutch monitoring system is described in copending U.S. patent application, Ser. No. 379,231, filed May 17, 1982, and a filter monitoring system is described in copending U.S. patent application, Ser. No. 378,703, filed May 17, 1982, all assigned to the assignee of the present invention. However, none of these monitoring systems provide an indication of the engine oil pressure in the vehicle. However, it has heretofore been common to monitor engine oil pressure in vehicles because of the critical dependence of engine operation upon sufficient engine oil pressure. Most such monitoring systems included oil pressure-actuated switches. However, such switches are designed to open or close at set pressure levels and are therefore likely to give misleading indications when low oil pressure is permissable due to low engine speeds or light loads. Furthermore, such switches can fail to inform the operator of hazardous oil pressure conditions at high engine speeds and high loads where the oil pressure is above the pressure threshold of the switch, but below what is required for safe, high-speed engine operation.
It has also been suggested to monitor engine oil pressure via analog pressure sensors and displays, as described in U.S. Pat. No. 3,906,437. However, such analog displays merely display the sensed oil pressure and therefore, the operator must rely upon his experience and judgement as to when a dangerous condition exists. Furthermore, such systems do not provide the needed warning signal when the sensed engine oil pressure exceeds an engine speed dependent threshold level.
Another alternative is disclosed in U.S. Pat. No. 3,723,964 wherein an alarm is energized when a difference signal derived from engine oil pressure and temperature sensors exceeds a signal from an engine speed sensor. However, this alternative requires four sensors for oil pressure, oil and ambient temperature and engine speed. Furthermore, it could produce unnecessary and misleading warning signals because it does not prevent generation of warning signals whenever the engine speed is below a predetermined non-zero cut-off level.